Synaptic transmission 2

Question 1

What are the two types of neurotransmitters?

Answer 1

Small molecule - simple AA’s or AA-like compounds

Large molecule - Peptides

Question 2

Where are small molecule neurotransmitters packaged?

Answer 2

Axon terminal

Proteins for synthesis are made in soma and sent to terminal

Question 3

Where are large molecule neurotransmitters packaged?

Answer 3

Synthesized and packaged in the soma

Completely filled vesicle is transported to the axon terminal

Question 4

What enzyme is responsible for ACh formation?

Answer 4

Acetylcholinetransferase

Located in axon terminal

Question 5

What are the three catecholamines and what amino acid are they derived from?

Answer 5

Dopamine, Norepinephrine, epinephrine

Derived from tyrosine

Question 6

What is the indoleamine and what amino acid is it derived from?

Answer 6

Serotonin

Tryptophan

Question 7

What is the imidazoline and what amino acid is it derived from?

Answer 7

Histamine

Derived from histidine

Question 8

What is the role of glycine?

Answer 8

Principle inhibitory neurotransmitter in the spinal cord

Question 9

What is the role of glutamate?

Answer 9

Principle excitatory neurotransmitter in the central nervous system

Question 10

What is the role of GABA?

Answer 10

Principle inhibitory neurotransmitter in the brain

Question 11

How does ATP function as a neurotransmitter?

Answer 11

Released an then cleaved to form adenosine

Adenosine acts as a sleep signal

Question 12

Describe nitric oxide as a neurotransmitter.

Answer 12

Membrane soluble gas

Synthesized directly in response to Ca influx, not stored in vesicles

Binds to cytosolic guanylyl cyclase in postsynaptic cells

Question 13

What is co-expression?

Answer 13

Many neurons release 2 neurotransmitters

Typically one small and one peptide

Question 14

What are the two types of neurotransmitter receptors?

Answer 14

Ionotropic - direct

Mtabotropic - indirect

Question 15

What are four important ionotropic receptors?

Answer 15

Nicotinic ACh receptor

GABAa

AMPA

NMDA glutamate receptor

Question 16

What is a postsynaptic potential?

Answer 16

Change in postsynaptic ion permeability caused by released neurotransmitter

Question 17

What is an excitatory postsynaptic potential (EPSP)?

Answer 17

Postsynaptic repsonse which increases the probability that postsynaptic neuron will fire an action potential

Generally depolarizes

Question 18

What is an inhibitory postsynaptic potential (IPSP)?

Answer 18

Postsynaptic response which decreases the probability that postsynaptic neuron will fire an action potential

May hyperpolarize

Question 19

How can an increase in conductance cause an EPSP?

Answer 19

Opens an ionotropic cation channel

Permeable to both Na and K ions

Sometime also Ca

Question 20

Describe the driving forces for Na and K at resting potential

Answer 20

Na is inward, K is outward

Na is many times larger than K driving force

Question 21

What is the net current flow when the cation channel is open?

Answer 21

The net current flow is inward and the cell will depolarize

Due to Na driving force being larger than K

Question 22

What is the amplitude of the EPSP dependent on?

Answer 22

The number of cation channels opened

Question 23

How can a decrease in conductance cause an EPSP?

Answer 23

Closing ion channels that normally hyperpolarize the membrane

This removes the hyperpolarizing influence

Question 24

What is an example of a receptor that causes an EPSP by decreasing conductance?

Answer 24

Muscarinic ACh receptor

M1, M3, M5

Question 25

How can an IPSP be caused by an increase in conductance?

Answer 25

Indirectly gated K channels Directly gated Cl channels

Question 26

What is the mechanism for Indirectly K channels?

Answer 26

Receptor activated G protein G-protein opens additional K channels in postsynaptic membrane GABAb, M2 and M4 mAChRs

Question 27

What does E(Cl) in order for the effect on the membrane to be inhibitory?

Answer 27

As long as E(Cl) is negative to threshold E.g. GABAa, glycine receptor

Question 28

How does the opening of directly gated chloride channels affect membrane potential?

Answer 28

Since E(Cl) and resting potential are very close, opening chloride channels stabilizes the membrane near the normal resting potential

Question 29

How can an IPSP be caused by conductance decrease?

Answer 29

Postsynaptic neuron contains Na/K permeable leak channels that are open in the resting membrane Metabotropic receptor closes these channels, removing a depolarizing influence Only happens at a specialized class of synapse in the reina